Carrier head and chemical mechanical polishing apparatus

ABSTRACT

Provided are a carrier head and a chemical mechanical polishing apparatus. The carrier head includes a body having a ring shape; a supporting unit surrounding the body; a retainer ring having a ring shape, the retainer ring surrounding the supporting unit; a membrane member on the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, the external ring having a hydrophobic surface.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2014-0094931, filed on Jul. 25, 2014, in the Korean Intellectual Property Office, and entitled: “Carrier Head and Chemical Mechanical Polishing Apparatus,” is incorporated by reference herein in its entirety.

BACKGROUND

1. Field

The present disclosure herein relates to a chemical mechanical polishing apparatus and a carrier head.

2. Description of the Related Art

A semiconductor device manufacturing process may include a deposition process of forming a thin-film layer on a wafer and an etching process of forming a fine circuit pattern on the thin-film layer. These processes may be repeated until a desired circuit pattern is formed on a wafer, and after the circuit pattern is formed, the wafer may have a rugged surface profile, for example, many convex and concave portions. A highly integrated semiconductor device may have a multi-layered structure and the number of convex and concave portions on a wafer surface and a height difference therebetween may be increased. Unevenness of the wafer surface may cause, for example, defocus in a photolithography process, and the wafer surface may be repeatedly polished for planarization.

SUMMARY

Embodiments may be realized by providing a carrier head, including a body having a ring shape; a supporting unit surrounding the body, e.g., liftably coupled to the body; a retainer ring having a ring shape, the retainer ring surrounding, e.g., disposed outside a bottom surface of, the supporting unit; a membrane member on, e.g., located on a lower portion of, the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, the external ring having a hydrophobic surface.

The external ring may include a metal frame.

The metal frame may be coated with a hydrophobic material.

The hydrophobic material may be a fluoride compound.

The hydrophobic material may be polytetrafluoroethylene (PTFE).

The external ring may support an outer surface of the membrane member, and an outer surface of the external ring and the outer surface of the membrane may be spaced apart from an inner surface of the retainer ring.

The membrane member may press against a substrate during a polishing process of the substrate; and a contact angle between a surface of the external ring and a drop of slurry supplied to the substrate during the polishing process may be 90° or more.

Embodiments may be realized by providing a chemical mechanical polishing apparatus, including a base, e.g., a base providing a lower structure; a platen, e.g., rotatably disposed, on the base and having a polishing pad on a surface, e.g., a top surface, thereof; a slurry supply arm adjacent to the platen and on the base, the slurry supply arm supplying slurry to a surface of the polishing pad; and a carrier head in co-operative relationship with the polishing pad, e.g., a carrier head pressing and supporting a substrate toward the polishing pad while a process is performed, the carrier head including a body having a ring shape; a supporting unit surrounding the body, e.g., liftably coupled to the body; a retainer ring having a ring shape, the retainer ring surrounding e.g., disposed outside a bottom surface of, the supporting unit; a membrane member on e.g., located on a lower portion of, the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, the retainer ring having a hydrophobic surface.

The slurry may include an oxide based compound.

A contact angle between a drop of the slurry and a surface of the external ring may be 90° or more.

The external ring may include a metal frame coated with a hydrophobic material.

The hydrophobic material may be a fluoride compound.

The fluoride compound may be polytetrafluoroethylene (PTFE).

The carrier head may further include a first hanging part protruding in a ring shape and having a first coupling surface on a surface, e.g., a top surface, thereof on an outer surface of the body, and a second hanging part vertically facing the first hanging part and having a second coupling surface on a surface, e.g., a bottom surface, thereof on an inner surface of the supporting unit.

The carrier head may further include a sealing film having one end fixed to the body under the first coupling surface and the other end fixed to the supporting unit under the second coupling surface.

Embodiments may be realized by providing a carrier head of a chemical mechanical polishing apparatus, the carrier head including a body having a ring shape; a supporting unit surrounding the body; a retainer ring having a ring shape, the retainer ring surrounding the supporting unit; a membrane member on the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, a contact angle between an exposed surface of the external ring and a drop of slurry being 90° or more.

The slurry may include an oxide based compound.

The slurry may include potassium hydroxide.

The slurry further may include abrasive particles.

The abrasive particles may include silica.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings in which:

FIG. 1 illustrates a plan view of a chemical mechanical polishing apparatus according to an embodiment;

FIG. 2 illustrates a perspective view of a portion of a polishing unit in FIG. 1;

FIG. 3 illustrates a cross-sectional view of a carrier head in FIG. 2;

FIG. 4 illustrates the carrier head supporting a wafer in a state that a supporting unit moves down relative to a body;

FIG. 5 illustrates a plan view of a polishing process being performed;

FIG. 6 illustrates a longitudinal sectional view of a carrier head in an area A of FIG. 5; and

FIG. 7 illustrates a slurry drop which is in contact with an external ring.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art.

In the drawing figures, shapes of the elements and dimensions of layers and regions may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.

FIG. 1 illustrates a plan view of a chemical mechanical polishing apparatus according to an embodiment. Referring to FIG. 1, a chemical mechanical polishing (hereinafter referred to as “CMP”) apparatus may include an index unit, a transfer robot 12, a polishing unit 13, and a cleaning device 14.

The index unit 11 may provide a space for storing a cassette C in which wafers W are accommodated. The index unit 11 may take the substrate, e.g., wafer W (see FIG. 4) out of, e.g., from, the cassette C and then may transfer the wafer W to the transfer robot 12 or may bring back, to the cassette C, the wafer W which has undergone a polishing process.

The transfer robot 12 may be disposed between the index unit 11 and the polishing unit 13 and may transfer the wafer W between the index unit 11 and the polishing unit 13.

FIG. 2 illustrates a perspective view of a portion of the polishing unit in FIG. 1. Referring to FIGS. 1 and 2, the polishing unit 13 may include a base 110, a load cup 120, a platen 130, and a carrier head assembly 140.

The base 110 may provide a lower structure of the polishing unit 13. The load cup 120 may be provided on a top surface of the base 110. The load cup 120 may be disposed adjacent to the transfer robot 12. The load cup 120 may provide a space where the substrate, e.g., wafer W (see FIG. 4) is temporarily on standby. An exchanger 121 may be provided on the top surface of the base 110 between the load cup 120 and the transfer robot 12. The wafer transferred from the index unit 11 by the transfer robot 12 may be placed on the exchanger 121, and the exchanger 121 may transfer the wafer W to the load cup 120.

The platen 130 may be provided singly or may be provided in plurality on the top surface of the base 110. When the platen 130 is provided in plurality, the platens 130 may be disposed on a circumference of the load cup 120. Each of the platens 130 may be rotatably connected to an upper portion of the base 110. For example, the platen 130 may be connected to a motor provided on the base 110. The polishing pad 131 may be disposed on a top surface of the platen 130, may be supported by the platen 130, and may be rotated together with the platen 130 while the process is performed. The polishing pad 131 may be provided with a plate shape having a predetermined thickness. The polishing pad 131 may directly contact and mechanically polish the wafer W, and may have a rough surface.

A pad conditioner 133 may be disposed adjacent to each of the platens 130 on the base 110. The pad conditioner 133 may maintain a state of the polishing pad 131, and the wafer may be effectively polished while the polishing process is performed.

A slurry supply arm 132 may be disposed on the base 110, and may be adjacent to each of the platens 130. The slurry supply arm 132 may supply slurry including reactant, abrasive particles, and a chemical reaction catalyst onto the surface of the polishing pad 131. Deionized water for oxidation polishing may be used as the reactant. Silica for oxidation polishing may be used as the abrasive particles. Potassium hydroxide for oxidation polishing may be used as the chemical reaction catalyst.

The carrier head assembly 140 may include a carrier head 141, a driving shaft 142, and a driving motor 143.

The carrier head assembly 140 may be disposed above the platen 130 and the load cup 120. The carrier head 141 may adsorb and fix the wafer W, a surface of the wafer W to be polished may face the polishing pad 131, and the carrier head 141 may press the wafer W against the polishing pad 131 while the process is performed. The driving motor 143 may provide a power allowing the carrier head 141 to rotate while the process is performed. The driving motor 143 and the carrier head 141 may be connected by the driving shaft 142. The number of the carrier head 141 may correspond to those of the platen 130 and the load cup 120. The carrier head 141 may be connected to a supporting frame. The supporting frame may sequentially transfer the carrier head 141 from the load cup 120 to each of the platens 130, and each of the carrier heads 141 may polish the wafer W while moving along one or more platens 130 after loading the wafer W from the load cup 120. Then, the wafer W which has undergone polishing may be unloaded to the load cup 120.

The cleaning device 14 may be disposed adjacent to the index unit 11 and the transfer robot 12. The wafer W, which is polished and then placed on the load cup 120, may be transferred to the cleaning device 14 through the exchanger 121 and the transfer robot 12. The cleaning device 14 may clean pollutant remaining on the polished wafer W. The cleaned wafer W may be brought back to the index unit 11 and accommodated in the cassette C, and then the polishing process is completed.

FIG. 3 illustrates a cross-sectional view of the carrier head 141 in FIG. 2, and FIG. 4 illustrates a carrier head 141 supporting a wafer in a state that the supporting unit moves down relative to a body. Referring to FIGS. 3 and 4, the carrier head 141 may include a body 1000, a supporting unit 2000, and a guide member 3000.

The body 1000 may provide upper and central structures of the carrier head 141. The body 1000 may be connected to the driving shaft 142 and rotated by a power provided by the driving motor. The body 1000 may have a substantially cylindrical shape. The body may have a hole 1200 vertically defined in the center thereof. The body 1000 may have different circumferences of top and bottom areas. For example, the body 1000 may include a first area 1110 disposed on an upper portion thereof and having a predetermined circumference; and a second area 1120 disposed on a lower portion thereof and having a circumference which is shorter than that of the first area 1110. The body 100 may further include a connection part 1130 disposed over the first area 1110 and connected to the driving shaft 142.

In an embodiment, the connection part 1130 may be removed and a top surface of the first area 1110 may be connected to the driving shaft 142.

The body 1000 may have a plurality of lower structures coupled thereto. For example, the body 1000 may include a first body 1010 and a second body 1020. The first body 1010 may form the connection part 1130. The second body 1020 may form the first area 1110 and the second area 1120. The first body 1010 may have a first stepped portion 1011 on a lower surface thereof, and the second body 1020 may have a second stepped portion 1021 which may be provided on a top surface thereof and of which shape corresponds to that of the first stepped portion 1011. The first body 1010 and the second body 1020 may be coupled in such a way that the first stepped part 1011 and the second stepped portion 1021 are engaged with and then fixed to each other. The first body 1010 may have a first hole 1210 corresponding to an upper portion of the hole 1200 at a central portion thereof, and the second body 1020 may have a second hole 1220 corresponding to a lower portion of the hole 1200 at a central portion thereof.

The body 1000 may have a monolithic structure.

A first hanging part 1111 may be provided on an outer surface of the body 1000. The first hanging part 1111 may be provided on a lower outer surface of the first area 1110. The first hanging part 1111 may outwardly protrude from the lower outer surface of the first area 1110 in the shape of a ring. A top surface of the first hanging part 1111 may be provided as a first coupling surface 1112. The first coupling surface 1112 may support the supporting unit 2000, and separation of the supporting unit 2000 from the body 1000 may be prevented. The first coupling surface 1112 may be parallel to the ground.

The supporting unit 2000 may be liftably coupled to the body 1000, and may surround side and lower portions of the body 1000. The supporting unit 2000 may have a substantially ring shape. The supporting unit 2000 may be divided into an upper supporting area 2100 and a lower supporting area 2200. An inner surface of the upper supporting area 2100 may have a shape corresponding to that of an outer surface of the first area 1110. When the supporting unit 2000 is coupled to the body 1000, the inner surface of the upper supporting area 2100 may be spaced apart from the outer surface of the first area 1110 by a predetermined distance.

A second hanging part 2110 may be provided on an inner surface of the supporting unit 2000. The second hanging part 2110 may be disposed to face the first hanging part 1111 in such a way that the second hanging part 2110 and the first hanging part 111 are vertically arranged, and separation of the supporting unit 2000 from the body 1000 may be prevented. The second hanging part 2110 may protrude inwardly from an upper inner surface of the upper supporting area 2100. The second hanging part 2110 may have a ring shape. The first hanging part 2110 may have an inner circumference corresponding to an outer circumference of the first area 1110. A bottom surface of the second hanging part 2110 may be provided as a second coupling surface 2111. The second coupling surface 2111 may be parallel to the ground.

A guide member 3000 may guide vertical movement of the supporting unit 2000.

The guide member 3000 may include a guide part 3100, a connection part 3200, and a coupling part 3300.

The guide part 3100 may have a cylindrical shape in which a central flow path 3110 is defined at the center thereof. The guide member 3000 may be slidably inserted into the hole 1200. The guide member 3000 may have an outer surface circumference corresponding to an inner surface circumference of the hole 1200.

The connection part 3200 may extend outwardly from a lower end of the guide part 3100. The connection part 3200 may have a ring shape. The connection part 3200 may be gradually inclined upwards from a central portion to the outside.

The coupling part 3300 may extend upwardly from an outer top surface of the connection part 3200. The coupling part 3300 may be fixed to the supporting unit 2000. For example, an insertion part 3310 outwardly extending may be provided on an outer surface of the coupling part 3300. The insertion part 3310 may have a rod shape, or have a ring shape provided along a circumference of the coupling part 3300. The insertion part 3310 may be fixed to the supporting unit 2000, and may be inserted into an inner surface of the supporting unit 2000. The insertion part 3310 may be inserted into an inner surface of the lower supporting area 2200.

A chamber 1300 may be disposed between the lower portion of the body 1000 and the inner surface of the supporting unit 2000. The chamber 1300 may be sealed from the outside. For example, a sealing film 1310 may be provided for sealing between an outer surface of the first area 1110 and an inner surface of the upper supporting area 2100. The sealing film 1310 may be a ring-shaped film which is made of a flexible material. An inner end of the sealing film 1310 may be fixed to the first area 1110 and an outer end of the sealing film 1310 may be fixed to an upper supporting area 2100. The sealing film 1310 may be fixed under the first coupling surface 1112 and the second coupling surface 2111.

An inner lower portion of the chamber 1300 may be sealed by the guide member 3000. For example, an outer surface of the guide part 3100 may be provided close to an inner surface of the hole 1200, the connection part 1130 may be connected to an inner surface of the supporting unit 2000, and the inner lower portion of the chamber 1300 may be sealed.

The chamber 1300 may be used to allow the supporting unit 2000 to move up and down relative to the body 1000. An up-and-down flow path 1410 connected to the chamber 1300 may be defined in the body 1000. The up-and-down flow path 1410 may be used to supply a gas to the chamber 1300 and exhaust a gas in the chamber 1300 to the outside. When the gas in the chamber 1300 is exhausted through the up-and-down flow path 1410, the supporting unit 2000 may move up relative to the body 1000 by a vacuum pressure formed in the chamber 1300. When the gas is supplied to the chamber 1300 through the up-and-down flow path 1410 and an internal pressure of the chamber 1300 is increased, the supporting unit 2000 may move down relative to the body 1000 until the second coupling surface 2111 is brought into contact with the first coupling surface 1112.

A membrane member 4000 may be provided on a bottom surface of the supporting unit 2000. The membrane member 4000 may be fixed to the supporting unit 2000 by fixing members 4100, 4200, and 4300 which have a ring shape and extend upwardly from a top surface thereof. The fixing members 4100, 4200, and 4300 may be concentrically provided around the center of the membrane member 4000. The fixing members 4100, 4200, and 4300 may include a central fixing part 4200 disposed adjacent to the center of the membrane member 4000, an outer fixing part 4100 disposed adjacent to an outer end of the membrane member 4000, and one or more auxiliary fixing part 4300 provided between the central fixing part 4200 and the outer fixing part 4100. Each of the auxiliary fixing part 4300 and the outer fixing part 4100 may be fixed to a lower portion of the supporting unit 2000 to provide lower chambers 1310 between the supporting unit 2000 and the membrane member 4000. The lower chambers 1310 may be provided in plurality by being partitioned between the outmost auxiliary fixing part 4300 and the outer fixing part 4100, and between the auxiliary fixing parts 4300. The lower chambers 1310 may be connected to first flow paths 1420 defined in the body 1000 and the supporting unit 2000. Even though the first flow path 1420 is singly illustrated in FIG. 3, one or more of the first flow paths 1420 may be connected to each of the lower chambers 1310. Through each of the first flow paths 1420, a gas may be supplied to the lower chamber 1310, and the membrane member 4000 may be allowed to press the wafer while the process is performed. One or more grooves 2300 having a ring shape may be defined in a bottom surface of the supporting unit 2000. When a gas in the lower chamber 1310 is exhausted through the first flow path 1420, the wafer may be adsorbed to the membrane member 4000 through a vacuum pressure formed by the groove 2300.

The central fixing part 4200 may be insertedly fixed between the inner surface of the supporting unit 2000 and the guide member 3000 to increase sealing properties of the chamber 1300. The central fixing part 4200 may be fixed to a lower portion of the supporting unit 2000 or a lower portion of the guide member 3000. A central chamber 1320 provided inside the central fixing part 4200 may be connected to a central flow path 3110. The central flow path 3110 may supply a gas to the central chamber 1320, and the membrane member 4000 may press the wafer W while the process is performed.

An external ring 4400 may be provided on an outer surface of the membrane member 4000. The external ring 4400 may be disposed on an outer surface of the outer fixing part. The external ring 4400 may have a predetermined stiffness and may support the outer surface of the membrane member 4000. A frame of the external ring 4400 may be made of metal. For example, the frame of the external ring 4400 may be made of stainless steel. The external ring 4400 may prevent a lateral expansion of an outer surface of the membrane member 4000 when the membrane member 4000 is expanded by supplying a gas into the lower chambers 1310, and the membrane member 4000 may primarily expand downwardly and effectively press the wafer.

The surface of the external ring 4400 may be hydrophobic-coated. For example, the external ring 4400 may be coated with a fluoride compound. The fluoride compound coated on the external ring 4400 may be polytetrafluoroethylene (PTFE).

A retainer ring 5000 may be provided outside a bottom surface of, e.g., surrounding, the supporting unit 2000. The retainer ring 5000 may have a ring shape, and may be disposed outside the membrane member 4000, e.g., the membrane member 4000 may be located within an inner circumference of the retainer ring 5000. The retainer ring 5000 may prevent separation of the wafer W from the carrier head 141 while the process is performed.

One or more supply grooves 5100 connecting outer and inner sides of the retainer ring 5000 may be defined in a bottom surface of the retainer ring 5000. Slurry supplied by a slurry supply arm 132 may be introduced to the wafer W through the supply groove 5100.

An inner surface of the retainer ring 5000 may be spaced apart from the external ring 4400 and a side surface of the membrane member 4000 by a predetermined distance. The membrane member 4000 may be prevented from contacting the retainer ring 5000 during expansion, and damage to the membrane member 4000 caused by contact friction may be prevented.

FIG. 5 illustrates a plan view of a polishing process being performed. Referring to FIG. 5, the polishing process may be performed while the platen and the carrier head 141 supporting the wafer on a bottom surface thereof are rotating.

The carrier head 141 may rotate while pressing the wafer against the polishing pad 131. The carrier head 141 may rotate in the same direction as a rotational direction of the platen. The carrier head 141 may change its position with respect to a top surface of the polishing pad 131 during the polishing process. For example, the carrier head 141 may repeatedly move within a predetermined region in a radial direction of the polishing pad 131.

The slurry supply arm 132 may supply slurry to a top surface of the polishing pad 131 at a position spaced apart from the carrier head 141. The slurry may be supplied into the retainer ring 5000 according to rotation of the platen. A pad conditioner may maintain a state of the polishing pad 131 at a position spaced apart from the carrier head 141. The pad conditioner may maintain a state of the polishing pad 131 while being changed in position.

FIG. 6 illustrates a longitudinal sectional view of a carrier head 141 in an area A of FIG. 5. Referring to FIG. 6, the slurry supplied into the retainer ring 5000 may be supplied to a bottom surface of the wafer W. Slurry may be partially introduced into a gap between a side surface of the membrane member 4000 and an inner side of the retainer ring 5000. If the slurry introduced into the gap separates during a polishing process after solidifying, polishing of the wafer W may become non-uniform.

FIG. 7 illustrates a slurry drop contacting the external ring 4400. Referring to FIG. 7, since the external ring 4400 is made of a hydrophobic material, a contact angle (0) between the external ring 4400 and the slurry drop may be greater than that between the slurry drop and a metal that is not coated. For example, the contact angle (0) between the external ring 4400 and the slurry drop may be 90° or more. The contact angle (θ) may become greater when the slurry contains an oxide based compound.

As the contact angle (θ) increases, a contact area between the slurry drop and the external ring 4400 may decrease. As the contact area between the slurry and the external ring 4400 decreases, slurry introduced into the gap may not become attached to the external ring 4400 and subsequently fall down, for example, due to gravity. According to embodiments, a phenomenon that slurry introduced into the gap becomes attached to the external ring 4400 and then falls down after solidifying after an elapse of time may be prevented.

According to an embodiment, the slurry introduced between an outer surface of the membrane member 4000 and an inner surface of the retainer ring 5000 may be prevented from being attached to the external ring 4000. Contamination of surroundings of the external ring 4400 caused by slurry may be prevented. Additional operation(s) for cleaning the surroundings of the external ring 4400 may be not necessary, or the number of the cleaning operation may be significantly reduced. Replacement of the external ring 4400 caused by pollution of the external ring 4400, for example, due to slurry attachment may be unnecessary, or a cycle of the replacement of the external ring 4000 may become longer.

By way of summation and review, various surface planarization techniques may be used to planarize a wafer surface. A chemical mechanical polishing apparatus may provide excellent planarization in a wide area and a narrow area, and may be used. A chemical mechanical polishing apparatus may include a carrier head pressing the wafer against a polishing pad while supporting the wafer.

According to an embodiment, a carrier head may efficiently support a wafer during a polishing process, and a chemical mechanical polishing apparatus may include the carrier head.

Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims. 

What is claimed is:
 1. A carrier head, comprising: a body having a ring shape; a supporting unit surrounding the body; a retainer ring having a ring shape, the retainer ring surrounding the supporting unit; a membrane member on the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, the external ring having a hydrophobic surface.
 2. The carrier head as claimed in claim 1, wherein the external ring includes a metal frame.
 3. The carrier head as claimed in claim 2, wherein the metal frame is coated with a hydrophobic material.
 4. The carrier head as claimed in claim 3, wherein the hydrophobic material is a fluoride compound.
 5. The carrier head as claimed in claim 3, wherein the hydrophobic material is polytetrafluoroethylene (PTFE).
 6. The carrier head as claimed in claim 1, wherein: the external ring supports an outer surface of the membrane member, and an outer surface of the external ring and the outer surface of the membrane are spaced apart from an inner surface of the retainer ring.
 7. The carrier head as claimed in claim 1, wherein: the membrane member presses against a substrate during a polishing process of the substrate; and a contact angle between a surface of the external ring and a drop of slurry supplied to the substrate during the polishing process is 90° or more.
 8. A chemical mechanical polishing apparatus, comprising: a base; a platen on the base and having a polishing pad on a surface thereof; a slurry supply arm adjacent to the platen and on the base, the slurry supply arm supplying slurry to a surface of the polishing pad; and a carrier head configured to press and support the polishing pad while operating, the carrier head including: a body having a ring shape; a supporting unit surrounding the body; a retainer ring having a ring shape, the retainer ring surrounding the supporting unit; a membrane member on the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, the retainer ring having a hydrophobic surface.
 9. The chemical mechanical polishing apparatus as claimed in claim 8, wherein the slurry includes an oxide based compound.
 10. The chemical mechanical polishing apparatus as claimed in claim 8, wherein a contact angle between a drop of the slurry and a surface of the external ring is 90° or more.
 11. The chemical mechanical polishing apparatus as claimed in claim 8, wherein the external ring includes a metal frame coated with a hydrophobic material.
 12. The chemical mechanical polishing apparatus as claimed in claim 11, wherein the hydrophobic material is a fluoride compound.
 13. The chemical mechanical polishing apparatus as claimed in claim 12, wherein the fluoride compound is polytetrafluoroethylene (PTFE).
 14. The chemical mechanical polishing apparatus as claimed in claim 8, the carrier head further including: a first hanging part protruding in a ring shape and having a first coupling surface on a surface thereof on an outer surface of the body, and a second hanging part vertically facing the first hanging part and having a second coupling surface on a surface thereof on an inner surface of the supporting unit.
 15. The chemical mechanical polishing apparatus as claimed in claim 14, the carrier head further including a sealing film having one end fixed to the body under the first coupling surface and the other end fixed to the supporting unit under the second coupling surface.
 16. A carrier head of a chemical mechanical polishing apparatus, the carrier head comprising: a body having a ring shape; a supporting unit surrounding the body; a retainer ring having a ring shape, the retainer ring surrounding the supporting unit; a membrane member on the supporting unit and within an inner circumference of the retainer ring; and an external ring on an outer surface of the membrane member, a contact angle between an exposed surface of the external ring and a drop of slurry being 90° or more.
 17. The carrier head as claimed in claim 16, wherein the slurry includes an oxide based compound.
 18. The carrier head as claimed in claim 16, wherein the slurry includes potassium hydroxide.
 19. The carrier head as claimed in claim 18, wherein the slurry further includes abrasive particles.
 20. The carrier head as claimed in claim 19, wherein the abrasive particles include silica. 